installer: T7036: handle missing version data in images gracefully

Author: dmbaturin

src/op_mode/image_installer.py

@@ -46,8 +46,12 @@
 MSG_ERR_LIVE: str = 'The system is in live-boot mode. Please use "install image" instead.'
 MSG_ERR_NO_DISK: str = 'No suitable disk was found. There must be at least one disk of 2GB or greater size.'
 MSG_ERR_IMPROPER_IMAGE: str = 'Missing sha256sum.txt.\nEither this image is corrupted, or of era 1.2.x (md5sum) and would downgrade image tools;\ndisallowed in either case.'
-MSG_ERR_ARCHITECTURE_MISMATCH: str = 'Upgrading to a different image architecture will break your system.'
+MSG_ERR_INCOMPATIBLE_IMAGE: str = 'Image compatibility check failed, aborting installation.'
+MSG_ERR_ARCHITECTURE_MISMATCH: str = 'The current architecture is "{0}", the new image is for "{1}". Upgrading to a different image architecture will break your system.'
 MSG_ERR_FLAVOR_MISMATCH: str = 'The current image flavor is "{0}", the new image is "{1}". Upgrading to a non-matching flavor can have unpredictable consequences.'
+MSG_ERR_MISSING_ARCHITECTURE: str = 'The new image version data does not specify architecture, cannot check compatibility (is it a legacy release image?)'
+MSG_ERR_MISSING_FLAVOR: str = 'The new image version data does not specify flavor, cannot check compatibility (is it a legacy release image?)'
+MSG_ERR_CORRUPT_CURRENT_IMAGE: str = 'Version data in the current image is malformed: missing flavor and/or architecture fields. Upgrade compatibility cannot be checked.'
 MSG_INFO_INSTALL_WELCOME: str = 'Welcome to VyOS installation!\nThis command will install VyOS to your permanent storage.'
 MSG_INFO_INSTALL_EXIT: str = 'Exiting from VyOS installation'
 MSG_INFO_INSTALL_SUCCESS: str = 'The image installed successfully; please reboot now.'
@@ -707,25 +711,42 @@ def validate_compatibility(iso_path: str) -> None:
     Args:
         iso_path (str): a path to the mounted ISO image
     """
-    old_data = get_version_data()
-    old_flavor = old_data.get('flavor', '')
-    old_architecture = old_data.get('architecture') or cmd('dpkg --print-architecture')
+    current_data = get_version_data()
+    current_flavor = current_data.get('flavor')
+    current_architecture = current_data.get('architecture') or cmd('dpkg --print-architecture')
 
     new_data = get_version_data(f'{iso_path}/version.json')
-    new_flavor = new_data.get('flavor', '')
-    new_architecture = new_data.get('architecture', '')
+    new_flavor = new_data.get('flavor')
+    new_architecture = new_data.get('architecture')
 
-    if not old_architecture == new_architecture:
-        print(MSG_ERR_ARCHITECTURE_MISMATCH)
+    if not current_flavor or not current_architecture:
+        # This may only happen if someone modified the version file.
+        # Unlikely but not impossible.
+        print(MSG_ERR_CORRUPT_CURRENT_IMAGE)
         cleanup()
         exit(MSG_INFO_INSTALL_EXIT)
 
-    if not old_flavor == new_flavor:
-        print(MSG_ERR_FLAVOR_MISMATCH.format(old_flavor, new_flavor))
+    success = True
+
+    if current_architecture != new_architecture:
+        success = False
+        if not new_architecture:
+            print(MSG_ERR_MISSING_ARCHITECTURE)
+        else:
+            print(MSG_ERR_ARCHITECTURE_MISMATCH.format(current_architecture, new_architecture))
+
+    if current_flavor != new_flavor:
+        success = False
+        if not new_flavor:
+            print(MSG_ERR_MISSING_FLAVOR)
+        else:
+            print(MSG_ERR_FLAVOR_MISMATCH.format(current_flavor, new_flavor))
+
+    if not success:
+        print(MSG_ERR_INCOMPATIBLE_IMAGE)
         cleanup()
         exit(MSG_INFO_INSTALL_EXIT)
 
-
 def install_image() -> None:
     """Install an image to a disk
     """